Search Results (234)

Ambient heat exposure reduces male fertility in mammals with scrotal testes. Our previous work has demonstrated that some stallions are more susceptible to ambient heat-related subfertility than others, yet the mechanism for heat-induced subfertility remains uncertain, limiting both diagnosis and preventative measures. This study sought to define how the phenotype of stallions susceptible to heat-induced subfertility differs from that of more resilient animals, by measuring the systemic (blood plasma) and localized (reproductive tract) inflammatory and oxidative stress markers of sperm concentration, sperm motility assessments, total antioxidant capacity (TAC; in blood and seminal plasma), malondialdehyde (MDA; in blood and seminal plasma), oxidized guanine species (8-OH-2dG; in blood plasma and spermatozoa DNA), sperm DNA damage (assessed via Halo, SCSA (Sperm Chromatin Structure Assay) and CMA3 (Chromomycin A3)), and c-reactive protein (CRP; in blood plasma). Post-breeding dismount semen samples (n = 357) and blood plasma samples (n = 97) were collected from 31 stallions at commercial thoroughbred studs throughout one breeding season (NSW, Australia). A subset of stallions (16%) was deemed heat-induced subfertility-susceptible (HISS) stallions. These animals showed reduced seminal plasma antioxidant capacity, increased systemic and localized lipid peroxidation, and distinct systemic inflammatory response. Seminal antioxidant capacity was found to be strongly associated with impaired sperm motility (r = 0.739 * vs. r = −0.059). The plasma c-reactive protein of heat-susceptible stallions correlated to heat exposure (r = 0.597 *) and affected sperm motilities (r = −0.527 **, r = −0.434 *). Systemic oxidative DNA damage (8-OH-2dG) also increased following heat events (r = 0.862 ***) and correlated with fertility losses (FCP: r = −0.740 **, PCP: r = −0.603 *). Non-HISS stallions displayed greater variability in systemic antioxidant status and robust response following heat exposure (r = 0.307 *) and localized antioxidant capacity was more strongly correlated to systemic antioxidant capacity than in the heat-susceptible group (r = 0.897 *** vs. r = 0.482 **). We demonstrate that impaired antioxidant responses, altered redox balance and suppressed acute-phase inflammatory signalling are key features associated with heat-induced subfertility in stallions and highlight biomarkers that could be used to identify animals with heat-susceptible fertility. Full article

Background: In horses, standing arthroscopy offers a valuable alternative to general anesthesia for the reduction of anesthetic-associated risks, and provides improved visualization in joints where access is facilitated by weightbearing. These techniques are particularly advantageous for patients with increased anesthetic risk or financial limitations. To the authors’ knowledge, the removal of osteochondral fragments from the distal interphalangeal joint in a standing, sedated horse using small-diameter arthroscopic equipment has not been previously reported. Case Presentation: A 7-year-old American Quarter Horse–Thoroughbred cross presented on referral for treatment of osteochondral fragmentation in the right fore distal interphalangeal joint. A standing arthroscopic approach to the distal interphalangeal joint was performed. In a weight-bearing position, debridement of the dorsal osteochondral fragments from the second and third phalanx was successfully completed, using a 2 mm NanoNeedle scope and 3.2 mm high-flow 10- degree cannula (Arthrex^®). At one year follow-up, the horse had returned to competition and was sound at veterinary examination. Conclusion: This case demonstrates the feasibility of standing NanoNeedle arthroscopy of the equine coffin joint with improved maneuverability, surgical ergonomics, and reduced iatrogenic injury compared to a standard rigid arthroscope. The successful execution of this technique effectively expands our collection of standing arthroscopic procedures in the equine patient. Full article

The aim of this study was to characterise the pedigree and genetic structure of Polish Sport Horses competing in Grand Prix show jumping events and to assess the implications for international sport horse breeding. Pedigrees of 513 horses were analysed, encompassing a total of 18,836 individuals over a maximum of 16 generations. The completeness and depth of the pedigrees allowed for a reliable estimation of inbreeding coefficients and genetic diversity. The mean inbreeding coefficient was low (0.645%), yet 82% of the horses exhibited some degree of inbreeding. The greatest loss of genetic variability was observed in non-founder generations, most likely due to the intensive use of a limited number of high-value stallions with domestic mares—a bottleneck effect. The most significant founders contributing to the population were the Thoroughbred stallions Ladykiller and Rantzau, as well as the Anglo-Arab stallion Ramzes, highlighting the international influence on the contemporary population. These findings emphasise the need for systematic monitoring of genetic diversity and the strategic use of pedigree data to minimise inbreeding and preserve the genetic potential of Polish Sport Horses for international breeding programmes. Full article

Physical exercise represents a physiological stressor capable of activating the acute-phase response (APR) in horses. However, the relative contribution of exercise intensity versus duration to acute-phase protein (APP) dynamics remains incompletely defined. This study compared the effects of short, high-intensity gallop exercise (2400 m flat race; n = 12) and prolonged, low-intensity endurance exercise (40 km; n = 13) on serum amyloid A (SAA), haptoglobin (Hp), and ceruloplasmin (Cp) in Thoroughbred racehorses. Blood samples were collected before exercise and at defined post-exercise time points. Between-group comparisons were performed at shared time points (72 h and 96 h post-exercise) using mixed-effects modeling and effect size analysis. The significant Group × Time interaction for SAA indicates that exercise duration plays a key role in determining the magnitude and persistence of the late-phase systemic inflammatory response. Serum amyloid A emerged as the most sensitive biomarker of cumulative physiological stress following prolonged exercise. These findings support the use of SAA monitoring during recovery to assist training management in equine athletes. Because early post-exercise sampling was not performed in the gallop group, conclusions primarily reflect differences in late-phase (72–96 h) APP kinetics. Full article

There are limited data on sequential computed tomographic (CT) evaluation and objective CT assessment of the metacarpal condyles in Thoroughbred racehorses. This longitudinal study aimed to document changes in attenuation of the metacarpal condyles during the first two years of training and racing. Fan-beam CT examination of the metacarpophalangeal regions was performed on 40 non-lame Thoroughbred yearlings, and repeated four more times, approximately six months apart. Mean Hounsfield Unit (HU) measurements were obtained on sagittal reconstructions of the dorsal and palmar halves of the medial and lateral condyles and parasagittal grooves. One-way ANOVA with a post hoc Tukey’s Test was used to investigate differences between mean HU values over time at the different regions of interest. Multivariable mixed-effects linear regression models assessed the association between dorsal and palmar HU and potential explanatory variables. Mean HU increased significantly with training, especially during the first six months, with a maximal sequential mean increase found in the medial parasagittal groove (119.8 [95% confidence interval 85.3, 154.30], p < 0.001). Dorsal regions had higher HU than palmar regions, with the highest HU recorded in the dorsal aspect of the medial condyle at time 3 (mean HU 1120.1 ± 63.4). Condyles had higher HU than parasagittal grooves (p < 0.001), the palmar half of the right condyles had higher HU than the left (p = 0.045) and the dorsal aspect of the medial condyle had higher HU than the lateral (p < 0.001). An increasing number of race starts and higher body weight:height ratio were associated with higher HU (p < 0.001). The main limitation was the loss of horses to follow-up as the study progressed. In conclusion, density of most regions of the metacarpal condyles increased with time spent in training, reflecting adaption to racehorse training. Full article

Hair whorl patterns are usually used as a predictor of equine laterality, temperament and reactions to various environmental stimuli. Thus, temperament and motor laterality may be deducted in order to ease the daily work, training, handling and transportation of Thoroughbreds. We aimed to identify the number, position and orientation of hair whorl patterns to find the association between environment stimuli and the laterality, affability, trainability and anxiety of 81 individuals. We analyzed hair whorls with SPSS (Statistical Package for the Social Sciences) accompanied by a laterality paddock test and temperament questionnaire. All of our examined Thoroughbreds showed at least one circular whorl on their head. Mostly, the whorls were located on the top of the head. Compared to previous studies, the presence of linear whorls on the body was also high. We found that the counterclockwise head and clockwise whorls were associated with left and right front leg preference (p < 0.001). Full article

This study evaluated a 181-day finishing system for horses entering the Korean meat chain by comparing retired thoroughbred geldings and Belgian-crossbred geldings under identical management and an ad libitum forage-based total mixed ration. Ten geldings (n = 5 per group) were individually housed, with body weight and feed intake recorded monthly. After slaughter, carcass traits and meat quality grade were assessed, and longissimus thoracis et lumborum samples were analyzed for proximate composition. Belgian-crossbreds consumed more dry matter (18.68 vs. 13.60 kg DM/day), corresponding to 2.3% vs. 2.4% of body weight, but showed markedly greater growth (average daily gain 1.063 vs. 0.290 kg/day) and higher gain-to-feed (0.059 vs. 0.024) than retired Thoroughbreds. Carcass weight and marbling-related traits favored Belgian-crossbreds, including higher intramuscular fat in longissimus thoracis et lumborum (9.15% vs. 3.22%). Despite higher total feed cost per head, the economic feed conversion ratio was substantially lower in Belgian-crossbreds (13,133 vs. 35,088 KRW/kg gain), resulting in a positive gross margin estimate, whereas retired Thoroughbreds showed a negative margin under the same system. These results suggest that meat-type horses may be better suited to short, intensive finishing, while alternative utilization or tailored finishing strategies may be needed for retired racehorses. Full article

Fractures are a leading cause of morbidity and mortality in Thoroughbred racehorses, posing a significant threat to their welfare and careers. This study introduces a deep learning model specifically designed to facilitate fracture detection in equine athletes. By leveraging extensive training on human fracture data and refining the model with equine imaging, it highlights the transformative potential of transfer learning across species and medical contexts. This approach is not limited to equine fractures but could be adapted for use in detecting injuries or conditions in other veterinary species and even human healthcare applications. A comprehensive databank of radiographs, sourced from public archives and equine hospitals, was curated to encompass diverse conditions (fracture and non-fracture), ensuring robust pattern recognition. The architecture integrates a Vision Transformer for global context modelling with a ResNet backbone and loss function to optimize local feature extraction and cross-species adaptability. The pipeline achieved 96.7% accuracy for modality classification, 97.2% accuracy for projection recognition, and fracture localization intersection over union values of 0.71–0.84 across equine datasets. This work bridges advancements in human and veterinary medicine, opening pathways for AI-driven solutions that extend beyond fractures, fostering improved diagnostic precision and broader applications across species (felines, canines, etc.). By integrating advanced imaging techniques with AI, this study aims to set a foundation for more comprehensive and versatile health monitoring systems. Full article

This retrospective report investigated whether starting racehorses’ training and racing early is associated with a less successful and a shorter racing career. The data of 600 Thoroughbred racehorses from the German Racehorse Association’s archiving programme were evaluated. The horses were classified into three groups regarding their different ages when starting training and racing: early training (16–24 months old)/early racing (two years old); early training/late racing (>two years old); and late training (25–30 months). Statistical models investigated effects on the horses’ length of career. The results showed that the length of their racing career was influenced by sex; geldings showed the longest career as they do not enter breeding programmes, and were analyzed separately. Geldings entering training early, with their first race at two years old, showed higher ratings and a similar length of racing career than those with their first race at three years old or more. Thus, early racing appeared to have had no negative effect on the length of the racing career or perseverance in racing in the geldings investigated. Further studies researching training effects and physiological resilience should consider alternative explanations for racing selection criteria (e.g., early maturation advantage and prior unsoundness) and the reason for ending a racing career. Full article

To investigate the factors affecting the utilization of retired Thoroughbred racehorses in equestrian disciplines, Bayesian linear mixed models were separately fitted using rank, round time, and obstacle faults from show-jumping competitions restricted to retired Thoroughbred racehorses as dependent variables, with the interaction between horse sex and the interval from race retirement to competition (as a proxy for transition training to show-jumping) as a fixed effect. When the interval was short (≤1 year), the estimated marginal mean of rank was statistically significantly lower in stallions (0.26) than in mares (0.41) and geldings (0.39). However, ranking improved with longer intervals in all sexes, with the greatest improvement observed in stallions, and the significant sex-related differences disappeared at the 3-year interval, suggesting an effect of transition training on ranking. Round time improved significantly with longer intervals in all sexes, consistent with the ranking pattern; significant improvement in obstacle faults was observed only in stallions and geldings. The explanatory power of the models, including major random effects, rider, horse ability, sire and affiliation after retirement, was moderate (conditional R²: 0.40–0.65), whereas that of the fixed effects was small (marginal R²: 0.02–0.07), indicating the multifactorial nature of success in competition. Full article

The genetic diversity and population structure of Tunisian Arabian horses were assessed using highly polymorphic microsatellite markers, which are critical for conservation and breeding programs. Despite the cultural and economic importance of Arabian horses in Tunisia, molecular data supporting their management remain limited. In this study, DNA from 130 horses was genotyped with 17 ISAG-FAO-recommended microsatellites to evaluate diversity within Eastern and Western Arabian lineages and their relationship to Thoroughbreds. Eastern Arabians showed an average of 5.176 alleles per locus, observed heterozygosity of 0.657, expected heterozygosity of 0.677, and a fixation index of 0.028, while Western Arabians displayed 5.941 alleles, heterozygosity values of 0.689 (Ho) and 0.688 (He), and a fixation index of −0.006. Genetic differentiation was low between Eastern and Western Arabians (0.011) but moderate between Eastern Arabians and Thoroughbreds (0.071), with high gene flow within Arabian subpopulations (0.950). Principal component analysis confirmed distinct subpopulations. These findings highlight high genetic diversity in Western Arabians and variable heterozygosity in Eastern Arabians, providing a molecular basis for targeted breeding strategies to preserve genetic traits, control inbreeding, and ensure the long-term sustainability of Tunisian Arabian horse populations. Full article

Thoroughbred race performance is influenced by genetics, training, recovery, and management, but decisions about race readiness are often subjective and lack validated physiological markers. This study evaluated thiol-oxidised albumin, a blood-based indicator of oxidative stress, as a potential biomarker of pre-race fitness in Australian Thoroughbreds. Seventy-five clinically healthy racehorses from seven stables were monitored across 216 competitive events (150 races, 66 trials). Blood samples were collected from the jugular at baseline, 48 h pre-race, and for each day up to 8 days post-race to examine levels of thiol-oxidised using the OxiDx test. At baseline, thiol-oxidised albumin levels were stable, but 24% of horses exhibited oxidative stress before racing, rising to 53% after three consecutive races. Thiol-oxidised albumin levels also remained increased for at least 8 days post-race. Statistical analyses were conducted in GraphPad Prism 10.6 using paired t-tests or repeated-measures one-way ANOVA with Dunnett’s post hoc test, alongside a generalised estimating equation model to assess associations with ordinal variables; significance was set at p < 0.05. Reference change values were calculated to determine thresholds for biologically meaningful changes in thiol-oxidised albumin levels. Increased pre-race oxidative stress was significantly associated with poorer finishing positions and lower trainer-perceived performance but was unrelated to horse age or sex. Horses without oxidative stress were more likely to finish in the top three. These findings demonstrate that oxidative stress prior to racing is common and adversely affects performance. Thiol-oxidised albumin represents a promising objective biomarker to guide training and racing strategies, with implications for both performance and equine welfare. Full article

Weaning represents a major developmental milestone for foals, especially when 4- to 7-month-old foals are abruptly separated from their dams. Studies have shown that the post-weaning period is associated with physiological and psychological stress, which may affect immune function. The present study aimed to describe and analyze the pattern of blood inflammatory biomarkers related to the innate immune system. A gradual foal–dam separation procedure was chosen, which included post-weaning social buffering by a familiar adult horse. Twelve Thoroughbred foals (six fillies, six colts) aged 4–6 months were enrolled and divided into a colt and a filly group, and after weaning, were kept as such. Blood samples were collected before and up to 7 days after weaning. Serum cortisol and cytokines (IL-2, IL-6, IL-10, TNF-α, IFN-γ) were quantified using equine-specific ELISA kits. Routine descriptive statistics were used to present the data, and inferences were drawn using a two-way repeated measures ANOVA. The level of significance was set at p < 0.05. Results showed significant differences in the concentrations of IL-10 (p < 0.001), IFN-γ (p < 0.01), and TNF-α (p < 0.01) on various days post-weaning. An apparent significant sex effect was not shown, but IL-10 peaked on day 3 in fillies. IFN-γ decreased significantly by day 5 in both sexes. Conversely, TNF-α levels increased significantly by day 5. No significant changes were observed for cortisol. Full article

Increased risk of musculoskeletal injury in galloping racehorses has been linked to decreased stride length and reduced speed over consecutive races prior to the injury. As racetrack curvature influences horses’ maximal speed, we hypothesized it also affects stride parameters. During training sessions, twenty-eight wagon-pulling Thoroughbred Chuckwagon horses were equipped with Global Navigation Satellite System (GNSS) loggers, allowing for identification of speed, stride length (SL) and stride frequency (SF), and average speed, SL and SF were calculated for consecutive 100 m sections. Effects of curvature on speed were investigated with a linear mixed model with speed as output variable, curvature as fixed factor, and horse as random factor. Effects of curvature and speed on stride parameters were investigated with linear mixed models with output variables SL and SF, continuous covariates speed, curvature, and the two-way interaction between curvature and speed as fixed factors, and horse as random factor. Curvature was associated with a significant increase in speed (p = 0.004), decrease in SL (p < 0.001) and increase in SF (p < 0.001), and for SL and SF the magnitude of these effects was dependent on speed (p < 0.001). At a curvature of 60° per 100 m, an increase in speed of 0.264 m/s was found compared to the straight, although this effect is likely confounded by fatigue. At the median speed of 14.5 m/s and a curvature of 60° per 100 m, a SF increase of 0.053 Hz (+2.4%) and a SL reduction of 0.137 m (−2.1%) was found compared to the straight. This is in the same order of magnitude as the 0.10 m SL reduction over consecutive races previously associated with increased injury risk. We conclude that, in Chuckwagon horses, interactions between speed and curvature are affecting stride parameters that have previously been identified as predictors of musculoskeletal injuries. Full article

Some correlations between serum Cu, Zn and Se and cytokines have been reported in humans. Especially, the Cu:Zn ratio corresponded with inflammation. To date, relationships between microelements and proinflammatory proteins are poorly understood in horses. The aim of the study was to evaluate whether Cu, Zn and Se may influence turnover of IL-6, IL-8 and tissue factor (TF) in breeding and working horses. Blood samples obtained from 66 horses were analysed. There were 37 pregnant broodmares of different breeds, 13 barren broodmares and 16 race Thoroughbred horses. Serum Cu, Zn and Se concentration was determined using the gas flame atomic absorption spectrometry (GFAAS) method. Plasma IL-6, IL-8 and TF concentration was determined by the ELISA method. A coefficient correlation was carried out to compare the values of microelements studied with IL-6, IL-8 and TF using Pearson’s test. The values of IL-6 correlated significantly positively with Se and Cu:Zn ratio, IL-8 correlated positively with Cu and Cu:Zn ratio and negatively with Zn, and TF correlated positively with Cu, Cu:Zn ratio and Se. The Cu:Zn ratio varies significantly between horses, with high values occurring in horses with high levels of proinflammatory proteins, which may indicate the presence of a subclinical inflammatory process. The high variability of TF in the studied groups gives hope for the use of its determination in laboratory diagnostics of horses. Full article